Wrinkles may be caused by a series of factors such as age, sun-induced damage, etc. but they are above all caused by facial expressions, i.e. repeated muscular contractions (expression of joy, anger, sadness, fear, surprise, etc.). They are therefore referred to as “expression wrinkles.” These wrinkles, which mainly appear on the upper half of the face, are caused by the interactions between the skin and the underlying muscles. In particular, vertical wrinkles appear on the forehead, as wrinkles known as “crow's feet” at the eye corners, horizontal wrinkles on the forehead, etc.
Thus, wrinkles on the forehead, as well as most chronic cephaleae, commonly known as “headaches” or “migraines,” are the result of prolonged tension that causes chronic contraction either of one of the three muscles of the upper part of the face: the forehead muscle (frontalis), the pair of muscles over the eyebrows (corrugators) and the pyramidal muscle of the nose (procerus), or even of several of them at the same time.
The pyramidal muscle is a fleshy little bundle of muscle located at the upper part of the back of the nose and between the eyes. It passes between the fascia covering the lower part of the nasal bone itself and the deep layer of skin in the area between the eyebrows. It draws the eyebrows downwards and towards the medial line, causing creases at the root of the nose. It is involved in frowning, the expression of concentration or simply to reduce dazzle in the case of bright light.
The forehead muscle is a flat muscle located under the skin of the forehead. It originates from the front edge of the epicranial aponeurosis and its fleshy fibres descend and attach to the deep layer of skin in the areas of the eyebrows and the area between the eyebrows. It raises the skin of the eyebrows and produces horizontal creases and wrinkles on the forehead.
Both eyebrow muscles pass on either sides of the glabella along the inner part of the superciliary arches. They originate from the inner edge of the superciliary arches and pass outwards along the arches to end in the deep layer of skin of the eyebrows. They draw the eyebrows towards the medial line and cause the vertical skin creases and wrinkles of the glabella.
Relaxing these muscles would therefore contribute to combat cephaleae and tension wrinkles. Moreover, relaxing these three muscles of the upper part of the face is likely to allow the activity of the muscles in the occipital zone to predominate. These muscles are the occipital muscle (occipitalis) and the two posterior auricular muscles (auricularis posterior).
This change of balance between facial muscles and occipital muscles in favour of the latter is likely to stretch the skin of the face, with the effect of a physiological facelift, which improves the appearance of the face.
Various treatments are already known in order to correct unsightly wrinkles such as wrinkles on the forehead or on the glabella, or crow's feet that appear on aging faces.
Some manufacturers of facial care creams recommend a suitable massage session to relax the facial muscles. However, one might doubt the effectiveness of such a treatment, above all if the expression wrinkles are already clearly marked.
There are also treatments for injecting products with a temporary action such as hyaluronic acid or type-A botulinic toxin, derived from the Clostridium botulinum bacterium (known by its commercial name Botox®). Botox® is injected at low doses into a specific muscle which becomes paralysed and therefore can no longer contract. These products have an active duration of a few months.
Permanent implants based on plastic microspheres or tubular implants made of PTFE, or alternatively collagen or silicone are also injected. The service life of these implants is several years. This relies on possibly reversible surgery.
However, these injection techniques entail a certain number of side effects such as the risk of developing an allergy or an oedema after injection, the risk of infection, red spots, bruises, irritations, etc.
Moreover, Botox® injections are in the patient's general circulation. One specific side effect is the undesirable paralysis observed in the muscles involved in swallowing (dysphagia).
In addition, muscular electro-stimulation is well known. Thus, for example, American U.S. Pat. No. 4,957,480 describes a method for toning the muscles and tissues of the face by stimulating the motor nerves and consequential contraction of the facial muscles, by applying galvanic currents of predetermined amplitude, frequency and polarity through electrodes moistened with a liquid solution of positively and negatively charged particles in order to insert it into the tissues so as to nurture the surrounding facial muscles and tissues. It is known from this document that it is possible, by this means, by the careful positioning of the electrodes directly on the muscle, to tire and consequently relax the forehead muscle, for example. The currents are between 300 and 640 μA with a frequency between 30 and 99 Hz, with alternating polarisation and an application time between 1 and 4 seconds, or even 10 seconds. The electric parameters used generate working fatigue similar to the muscle's voluntary fatigue, which produces only slight relaxation or none. This is the traditional field of electro-stimulation with frequencies lower than 100 Hz in order to produce short contractions.
American U.S. Pat. No. 3,709,228 describes a device for the electro-stimulation of the user's facial nerves and, consequently muscles, comprising a support resting on the nose and ears and having flexible arms that can extend in opposite directions and bear at their ends electrodes that contact the skin. A first electrode is positioned in order to stimulate the forehead branch of the facial nerve. A second electrode is positioned with a view to stimulate the maxillary branch of the facial nerve. Lastly, a third electrode is positioned with a view to stimulate the mandibular branch of the facial nerve. This document does not suggest the positioning of an electrode in the space between the eyebrows.